The electrocardiogram (ECG) presently is analyzed by several different methods. The measurement of the scalar representation of single leads is most common as seen in FIG. 1. The duration and voltage amplitudes of designated deflections, Q, R, S, etc., are measured. Combinations of abnormalities, which are measurements that exceed normal ranges found in selected leads, indicate an abnormality of the myocardium. For example, Q waves of 0.04xe2x80x3 duration in leads II, III, and AVF is interpreted as inferior myocardial infarction.
Most commonly the standard 12-lead ECG is analyzed in this way. This system of leads consists of 6 limb leads and 6 leads recorded from the precordial area of the chest as positioned in FIG. 2. These leads measure a voltage difference between a positive and a negative electrode or combinations of electrodes. A positive deflection is recorded when an electrical impulse is coming towards the lead and a negative deflection with the impulse going away from the lead. When looking at the combination of the voltage and duration deflections recorded on the ECG paper, they will provide a predictable pattern which may be analyzed for abnormality. To analyze the pattern, however, it is necessary to further divide the pattern into three different wave complexes: P, QRS, and T complexes (see FIG. 1). The P represents the depolarization of the atrium, QRS the depolarization of the ventricles, and T the repolarization of the ventricles. Different heights, width, and time intervals of the segments may be signs of a pathological condition.
Another method of ECG analysis utilizes three leads, X, Y, and Z, oriented respectively with the right/left, head/foot, and front/back axes of the body as seen in FIG. 3. With this system, two leads are analyzed together in anatomic planes of the torso, the X, Z in the horizontal plane, the X, Y in the frontal plan, and the Y, Z in the sagittal plane. The lead voltages are displayed as time interrupted loops as shown in FIG. 4, which is a horizontal plane display of a normal vectorcardiogram. The loops are analyzed by measuring certain dimensions found useful in diagnosing abnormalities of the myocardium.
In order to analyze each specific time point, it is first necessary to measure the total electrical activity of the heart emitted for a specific point in time. The algebraic sum of this measured electrical activity for that given moment in time will be called the Heart Vector, HV.
By deriving a median HV by finding the medians of the X, Y, and Z measurements from a sample of healthy volunteers, it is possible to compare an individual""s HV to this xe2x80x9cnormalizedxe2x80x9d HV. There will be defined borders that a normal HV will fall into and any HV that exceeds these borders will be a sign of abnormality. The deviation from median HV will be called the Vector of Deviation, VD. Alternatively, instead of using a grouping or sample of healthy volunteers, a grouping of persons having a specific condition or heart disease can be selected. In this case the individual""s HV is compared to the heart vectors of the grouping of persons having the specific condition.
The Vector of Abnormality, VA, is closely related to the Vector of Deviation. They both have the same direction and orientation but have different points of origin. For example, any vector beyond the 95th percentile may be defined as the VA. To make the VA as sensitive as possible, it is necessary to transfer the point of origin from (0,0) to the head of the median Heart Vector. The percentile limit surrounding the head of the median HV defines the outermost boundary of normality. We can precisely define the point of origin of VA at this boundary, called point Oa. The axes are rotated to achieve this sensitivity. The measured Vector of Abnormality will provide the first criteria used to classify an abnormal condition.
The second criteria used to classify an abnormal condition will be the Delta Vector, or V. The Delta Vector describes the relationship between two HV with respect to time. There is a xe2x80x9cnormalizedxe2x80x9d Delta Vector as there is a xe2x80x9cnormalizedxe2x80x9d HV, as described above. If the V is measured to be beyond a defined boundary, such as 95th percentile, it will indicate abnormality.
By looking at an abnormal vector, VA, as well as the HV""s with respect to time, the Delta Vector, it will be possible to characterize the type and severity of the cardiac abnormality. The device used to analyze this will consist of computer hardware for ECG computations and archives, software programs to analyze parameters, and the ability to store records of normal and abnormal populations employed in forming the group envelopes.
The method used in this patent is a mathematical approach and does not depend on a specified display of the ECG from which measurements are taken. It involves the simultaneous analysis of two to any number of leads.
It is the object of the invention to provide a method of analysis of the orthogonal three lead ECG to determine the presence of abnormality.
It is a further object to provide a device to analyze the orthogonal three lead ECG to determine the presence of abnormality.
Another object is to provide a method of analysis of the orthogonal three lead ECG to distinguish one abnormal condition from all others. A related object is to provide a device to analyze the orthogonal three lead ECG to distinguish one abnormal condition from all others.
Yet another object is to provide a method of analysis of multiple leads (two to any greater number) to determine the presence of abnormality and to distinguish one abnormal condition from all others. A related object is to provide a device to analyze multiple leads (two or more) to determine the presence of abnormality and to distinguish one abnormal condition from all others.
Still another object is to provide a method of analysis of the standard 12-lead ECG to determine the presence of abnormality and to distinguish one abnormal condition from all others.
Yet another object is to provide a method of analysis of regional leads (two or more lead vectors perpendicular to the wave propagation in a region of myocardium) to determine the presence of abnormality and to distinguish one abnormal condition from all others.
Another object is to provide a method of analysis of the ECG and a device to determine the presence of one or multiple abnormalities of the heart.